1. Field of the Invention
The present invention generally relates to solid fire starter materials which are ignitable by flint sparks. More particularly, this invention relates to fire starter materials employing magnesium as their chief combustible ingredient.
2. Description of the Prior Art
Various types of fire starters have been marketed for use by outdoorsmen, hunters, woodsmen and householders and others in igniting wood, charcoal and other materials, particularly when they are damp. Such fire starters have been made of such diverse materials as flammable chemicals in liquid or tablet form, elements such as zirconium or titanium in powdered forms, mixtures of wood particles and various resins, wax candles and various semi-solid chemical compounds sold in squeezable dispensing tubes.
Other fire starter materials have been based upon the ignition and burning characteristics of the element magnesium. Magnesium combines with oxygen to form magnesium oxide in the following highly exothermic reaction: EQU Mg+1/2 O.sub.2 MgO 143,940 cal./mole at 25.degree. C.
This reaction, burns with a dazzling white flame and produces a substantial amount of heat in the temperature range of 2700.degree. C., to 2900.degree. C. Because of the great amount of heat energy released by this reaction, only a very small amount of magnesium is need to kindle a fire. The prior art also discloses the use of various materials to control the burning characteristics of magnesium. That is to say, magnesium has been mixed, alloyed and compounded with various materials to control its burning characteristics when it is used in the context of fire starters.
However, despite the wide variety of fire starters now available, each type seems to have its own set of drawbacks.For example, most flammable chemical fire starters have one or more of the following disadvantages: (a) difficult ignition; (b) dangerous instability due to high flammability or low spontaneous ignition temperatures; (c) low burning temperatures; (d) short burning times; or (e) large volume requirements which make transport and storage difficult. Magnesium based fire starters overcome many of these disadvantages of the other chemical fire starters, but they are not without their own disadvantages. For example, many fire starters employing magnesium burn with a dazzling, but extremely short-lived, flame which often does not exist long enough to ignite the kindling material. Consequently various materials have been mixed with magnesium in order to better control its burning characteristics.
Most materials heretofore employed to control the above noted ignition and burning characteristics of magnesium have been elements, particularly those elements known as the rare earth elements. In this regard, the term "rare earths" usually implies the definition recommended by the Commission on Nomenclature of the International Union of Pure and Applied Chemistry. The Commission defines "rare earths" as consisting of those 17 element, namely, scandium, yttrium and the 15 elements having atomic numbers 57 through 71 for which the International Union recommends the term "Lanthanum Series". Aluminum, manganese, zinc, thorium and zirconium have also been widely used. It should also be noted in passing that many commercially available magnesium base alloys may also contain trace amounts of calcium copper, iron, nickel, and silicon. Such fire starter materials have been the subject of various patents.
For example, U.S. Pat. No. 3,402,029 teaches the use of misch metal to control the ignition and burning characteristics of a misch metal/magnesium alloy. The misch metal, which provides the sparking properties of the alloy, basically comprises the rare earth metals of cerium, lanthanum and praseodymium. Its most use is in the capacity as the pyrophoric substance employed in cigarette lighter flints.
U.S. Pat. No. 4,188,192 teaches a fire starter material comprised of a magnesium base alloy comprised of more than 50 percent by weight magnesium with the balance of the material being aluminum, manganese, zinc, thoranium, zirconium and/or the rare earths. Fire starter materials formed from such magnesium base/aluminum, manganese, zinc, thorium, zirconium, and/or the rare earths have good ignition qualities, but they are rather difficult to shave or whittle from the stock piece and also are, owing largely to the costs of their nonmagnesium ingredients, rather expensive.
The prior art has also recognized that some of the rare earth metals themselves, principally zirconium and titanium, in their pure or highly refined powder forms, have useful pyrophoric properties. They have been used as fulminators in flash bulbs and as ingredients in incendiary compositions for munitions to produce short bursts of intense heat or flame. However, such metal powders are generally recognized as being unsuitable for use in fire starter applications because of their tendency to flash-burn in short bursts measured in milliseconds. They also are characterized by low self-ignition temperatures which make them unstable and dangerous to handle. Nonetheless, U.S. Pat. No. 3,927,993 teaches how these dangerous characteristics can be overcome by the conjunctive use of low-grade zirconium sponge materials. However, these materials are both scarce and expensive.
Accordingly, there is still a need for more effective fire starter materials, especially those having all of the desirable characteristics of: small size, light weight, easy shavability of the stock piece, low cost, easy ignition (but with a high enough spontaneous ignition temperature to avoid accidental self-ignition), long burning time and high burning temperature.